Treatment as prevention is an effective method in control HIV infection. In populations with very high testing rates, a low proportion of people with HIV who are undiagnosed, and very high levels of ARV coverage and viral suppression, the effect of reducing the community viral load can start to be seen. The best evidence appears to come from San Francisco. Here amongst gay men, which in this city form 85 to 90% of the HIV-positive population, frequent testing, a low rate of undiagnosed cases, and high rates of ARV coverage have produced a 40% fall in the community viral load between 2004-2008, a fall in new diagnoses of 45%, and what appears to be a 33% decline in HIV incidence between 2006-2008. Similar falls have been seen as a result of an intensive testing and prevention campaign amongst injecting drug users in Vancouver, British Columbia, though this has not as yet been seen to be happening in the rest of the province. In March 2010, San Francisco became the second area after British Columbia to officially adopt a policy of aggressive expansion of testing, especially for underserved populations, and universal treatment regardless of CD4 count for those diagnosed.